A robot system in which workpieces are photographed by a camera and the position thereof is recognized thereby is now in practical use for carrying out an inspection job, assembly job, palletizing job and the like. The camera is fixed, or mounted on the hand of a robot, for this purpose, and in particular, when the position of the camera is fixed, assembly jobs and the like cannot be carried out if the position of the camera is dislocated.
The normal operation of the robot can be prevented by various causes, including, for example, the dislocation of the relative position of the robot and an object, and errors in a teaching program and the like.
Therefore, when a problem occurs, the elements which may be the cause of the problem must be individually checked, to specify the cause of the problem. Of course, the dislocation of the camera is one of the causes of the problem.
In general, although the frequency of dislocation of the position and attitude of a fixed camera is not high, a slight positional dislocation of the camera would disturb a robot job in which the camera is photographing a distant object. A slight amount of positional dislocation is difficult to easily determine, but when a job is carried out by using the robot without checking the positional dislocation thereof, the operator feels uneasy before the start of the job, as if a problem arises while the robot is being operated, workpieces and the like may be damaged, and this damage is difficult to recover.
Consequently, the positional dislocation of a camera, and the attitude thereof and the like, must be confirmed prior to the start of a job.